The present invention relates to a clamp used for removably connecting various fluid-conveying flexible hoses and the like to joints, valves, cocks and the like.
Generally speaking, such clamps used on hoses and the like are classified into three types, namely, a first type in which a single spring metal wire is wound into a pair of juxtaposed concentric rings so that the hose or the like is clamped either by the self-restoring resilient force of the circular rings or by a manual contracting force applied thereto at the opposite ends of the convolutions so as to reduce the ring diameter, a second type in which a non-spring metal strip is formed with a series of meshing holes and wound into a circular ring to serve as a worm wheel, while an operating threaded rod held on the circular ring by an attaching housing and serving as a worm is engaged with said meshing holes in the strip, so that manual rotation of the threaded rod reduces the circular ring diameter to clamp the hose or the like, and a third type in which a spring metal strip is wound into a circular ring, whose self-restoring resilient force tending to reduce the ring diameter is utilized to clamp the hose or the like.
In the third type of clamp, however, if it is formed by winding a spring metal strip of uniform thickness and width, the ring diameter, when expanded or contracted, generally assumes an oval or ellipse rather than a right circle because the bending rigidity becomes greater toward the cut ends (opposite terminal edges) of the circular ring. Therefore, if this is used to clamp the hose or the like, the circular ring will not act on the entire periphery of the hose or the like with uniform clamping force, so that there is a danger that the gas, such as air, flowing through the hose or the like will leak. Prevention of leakage of fluid must be said to be of utmost importance for the third type of clamp designed to clamp the hose or the like in a natural manner, namely, by the self-restoring resilient force or self-contracting force produced by winding a spring metal strip into a circular ring, unlike the second type of clamp designed to clamp the hose or the like by a manual operating force applied to the screw.
Therefore, conventionally, as will be fully described in connection with embodiments of the invention, in order to ensure uniform bending stress throughout the periphery of the circular ring while maintaining the uniform thickness and width of said spring metal strip, the central region of the strip is formed with triangular or other similar openings by a punch and die assembly. Such arrangement, however, makes the die and working implements correspondingly complicated because of the need of forming said openings and can hardly accomodate changes in the size of the products. Further, there is also a problem about the effective use of material. Further, in the developed or unfolded planar form of the long-sized strip after shearing operation, the right and left halves on both sides of the imaginary winding center line are not of the same or symmetrical simple shape, so that they differ in bending rigidity from each other. This, coupled with the fact that the inclined edges of the triangular openings are relatively short, makes the circular ring inferior in circularity, causing a problem that it is difficult to ensure uniform clamping force on the entire periphery of the hose or the like and smooth expanding operation on the circular ring.